U.S. patent number 7,712,502 [Application Number 12/057,978] was granted by the patent office on 2010-05-11 for in-process vision detection of flaw and fod characteristics.
This patent grant is currently assigned to The Boeing Company. Invention is credited to Roger W. Engelbart, Reed Hannebaum, Tim Pollock.
United States Patent |
7,712,502 |
Engelbart , et al. |
May 11, 2010 |
In-process vision detection of flaw and FOD characteristics
Abstract
An inspection system (9) includes an idler wheel (61) that is
coupled to a fabrication system (8) and is in contact with a
backing layer (65) of an applied material (64), A rotation sensor
(63) monitors the idler wheel (61) and generates a rotational
signal. A controller (24) is coupled to the rotation sensor (63)
and determines a characteristic of one or more flaws and FOD (19)
on a composite structure (12) in response to the rotation
signal.
Inventors: |
Engelbart; Roger W. (St. Louis,
MO), Hannebaum; Reed (Mount Vernon, IL), Pollock; Tim
(Ballwin, MO) |
Assignee: |
The Boeing Company (Chicago,
IL)
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Family
ID: |
36460631 |
Appl.
No.: |
12/057,978 |
Filed: |
March 28, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090000723 A1 |
Jan 1, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10904727 |
Nov 24, 2004 |
7424902 |
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Current U.S.
Class: |
156/351;
356/238.3; 356/237.4; 356/237.3; 356/237.1; 156/361 |
Current CPC
Class: |
B29C
70/38 (20130101); G01N 21/89 (20130101); G01N
2021/8472 (20130101) |
Current International
Class: |
B32B
41/00 (20060101); G01N 21/47 (20060101) |
Field of
Search: |
;156/64,351,361
;356/237.3,237.4,283.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0319797 |
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Jun 1989 |
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EP |
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0833146 |
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Jan 1998 |
|
EP |
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0903574 |
|
Jan 1998 |
|
EP |
|
1030172 |
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Aug 2000 |
|
EP |
|
1334819 |
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Aug 2003 |
|
EP |
|
1503206 |
|
Feb 2005 |
|
EP |
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2001012930 |
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Jan 2001 |
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JP |
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94/18643 |
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Aug 1994 |
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WO |
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2004/025385 |
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Mar 2004 |
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WO |
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Other References
Abandoned U.S. Appl. No. 10/628,691 entitled Systems and Methods
for Identifying Foreign Objects and Debris (FOD) and Defects During
Fabrication of a Composite Structure, inventor: Engelbart et al.,
filed Jul. 28, 2003. cited by other .
Expired U.S. Appl. No. 60/559,890, to Biornstad et al., filed Apr.
6, 2004. cited by other .
Expired U.S. Appl. No. 60/559,911, to Johnson et al., filed Apr. 4,
2004. cited by other .
Krupka, R; Walz, T; Ettemeyer, A: "Industrial Applications of
Shearography for Inspection of Aircraft Components" Proceedings of
the 8th European Conference of Nondestructicve Testing<
Barcelona (Spain), Jun. 17-21, 2002, 'Online! Jun. 30, 2002,
XP002351899 NDT.NET--Feb. 2003, vol. 8, No. 2 Retrieved from the
Internet: URL:http://www.ndt.net/articl/encndt02/484/484.htm>
'retrieved on Oct. 31, 2005! cited by other .
The Written Opinion for International Application
PCT/US2004/039905, dated May 25, 2005 6 pages. cited by other .
International Search Report dated May 25, 2005 for report for
International Application PCT/US2004/039905, dated Nov. 30, 2004, 4
pages. cited by other .
Prof. J. Zhang: "Angewandte Sensorik" CH. 4, Sensoren in Der
Robotik, Nov. 11, 2003; (retrieved from the Internet,
URL:http://tech-www.Informatik.uni-hamburgnsorik/vorlesung.sub.--03.pdf)
retrieved on Apr. 2004! p. 89, 20 pages. cited by other .
European Search Report, Application No. 04076900.2, dated Dec. 1,
2004, 4 pages. cited by other .
Fiedler, L., et al, "Tango Composite Fuselage Platform", SAMPE
Journal, vol. 39, No. 1, Jan./Feb. 2003, pp. 57-63. cited by other
.
Advanced Technology Tape Laying for Affordable Manufacturing of
Large Composite Structures;
http://www.cinmach.com/tech/pdf/TapeLayingGrimshaw.pdf; Michael N.
Grimshaw, et al; 11 pages. cited by other .
Fiber Placement;
http://www.cinmach.com/tech/pdf/asm.sub.--chapter.sub.--fp.pdf; Don
O. Evans; Cincinnati Machine; 3 pages. cited by other .
Automated Tape Laying;
http://www.cinmach.com/tech/pdf/Grimshaw%20ASM%20Handbook.pdf;
Michael N. Grimshaw; Cincinnati Machine; 6 pages. cited by other
.
Raytheon Aircraft's Hawker Horizon Reaches Fuselage Milestone,
Raytheon News Release;
http://www.beechcraft.de/Presse/2000/100900b.htm; 2 pages. cited by
other .
BAe 146, Flight International, May 2, 1981, 2 pages. cited by other
.
A Barrelful of Experience, Intervia, May 1992, 2 pages. cited by
other .
Raytheon, Mar. 2000, vol. 4, No. 2,
http://www.cs.com/king/vasci/newsletter/vol42.html, 2 pages. cited
by other .
Business Aviation, Jun. 7, 2002,
http://www.aviationnow.com/avnow/news/channel.sub.--busav.jsp?view=story&-
id=news/btoyo0607.xml, 1 page. cited by other .
Beechcraft's Composite Challenge,
http://www.aerotalk.com/Beech.cfm, 2 pages. cited by other .
Sharp et al., "Material Selection/Fabrication Issues for
Thermoplastic Fiber Placement", Journal of Thermoplastic Composite
Materials, vol. 8; Jan. 1995, p. 2-14. cited by other .
http://www.cinmach.com/WolfTracks4-1/MTG-WT7.htm; Premier I
Features Lighter, Stronger, All-Conmposite Fuselage, 1 page. cited
by other .
http://www.cinmach.com/compnews/PressReleases/pr00-11.htm; Raytheon
Aircraft Orders Four More Fiber Cincinnati Fiber Placement Systems
for Industry's First Composite-Fuselage Busines Jets, 1 page. cited
by other .
http://www.rockymountaincomposites.com/wind-sys.htm: Filament
Winding, 2 pages. cited by other .
Assembly Guidance Systems website at
http://www.assemblyguide.com/HAMPI/Hampi.htm, "automatic Ply
Verification", 2 pages, printed Oct. 17, 2005. cited by other .
UltraOptec, Inc. website at
http://www.ultraoptec.com/luis-747.html, "Luis 747", 17 pages,
printed Oct. 17, 2005. cited by other .
Lichtenwalner, P.F., Neural Network-Based Control for the Fiber
Placement Composite Manufacturing Process, Journal of Materials
Engineering and Performance, vol. 2(5), Oct. 1993, p. 687. cited by
other .
Wang, Eric L., Effects of Laps and Gaps on the Processing of
Advanced Thermoplastic Composites, Thesis, Massachusetts Institute
of Technology, Jan. 1991. cited by other .
Engelbart, Roger W., et al., In-Process Monitoring of Pre-Staged
Fiber Placement Tows Using Nuclear Magnetic Resonance (NMR),
Proceedings of the 43rd International SAMPE Symposium, Anaheim,
California, May 31-Jun. 4, 1998. cited by other .
Sharp, Richard, et al., Material Selection/Fabrication Issues for
Thermoplastic Fiber Placement, Journal of Thermoplastic Composite
Materials, vol, 8, pp. 2-7 (Technomic Publishing Co., Inc.). cited
by other .
Thomas, Matthew M. et al., Manufacturing of Smart Structures Using
Fiber Placement Manufacturing Processes; SPIE, vol. 2447, pp.
266-273 (1995). cited by other .
Elliott, Augustus W., Fiber Placement Inspection System and
Experimental Approach; 43d Int'l SAMPE Symposium, pp. 957-963
(Society for the Advancement of Material and Process Engineering)
(1998). cited by other .
R. Paulson et al., Infrared Imaging Techniques for Flaw Detection
in Composite Materials, Lockheed Missiles and Space Company, Inc.,
Sunnyvale, CA, pp. 88-95. cited by other.
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Primary Examiner: Koch, III; George R
Attorney, Agent or Firm: Yee & Associates, P.C. Poole;
James M.
Parent Case Text
RELATED APPLICATIONS
This application is a divisional of, and claims priority from,
prior application Ser. No. 10/904,727, filed Nov. 24, 2004 now U.S.
Pat. No. 7,424,902. Other related applications include U.S. patent
application Ser. Nos. 09/819,922; 10/846,974; and 10/904,719.
Claims
What is claimed is:
1. A fabrication system comprising: a lamination system comprising
a layer applicator applying a plurality of composite material
layers to a substrate to form a structure; and a flaw and foreign
object debris (FOD) inspection system proximate said lamination
system comprising; an idler wheel coupled to said lamination system
and contacting a backing layer of an applied material; a rotation
sensor monitoring said idler wheel and generating a rotational
signal; a detector detecting at least one flaw and FOD and
generating a flaw and FOD detection signal; and a controller
coupled to said rotation sensor and determining at least one
characteristic of said at least one flaw and FOD on said structure
in response to said rotation signal and said flaw and FOD
signal.
2. A fabrication system as in claim 1 wherein said controller
alters operation of the fabrication system in response to said at
least one characteristic.
3. A fabrication system comprising: a lamination system comprising
a layer applicator applying a plurality of composite material
layers to a substrate to form a structure; and a flaw and foreign
object debris (FOD) inspection system proximate said lamination
system comprising; at least one illumination device illuminating a
portion of the structure; at least one detector monitoring said
portion and detecting at least one flaw and FOD in said portion
during application of said plurality of composite material layers
in response to reflection of said light rays off of said portion
and generating a flaw and FOD detection signal; an idler wheel
coupled to said lamination system and contacting a backing layer of
an applied material; a rotation sensor monitoring said idler wheel
and generating a rotational signal; and a controller coupled to
said rotation sensor and determining at least one characteristic of
said at least one flaw and FOD in response to said rotation signal
and said flaw and FOD detection signal.
4. A fabrication system as in claim 3 wherein said controller
alters operation of the fabrication system in response to said at
least one characteristic.
Description
BACKGROUND INFORMATION
1. Technical Field
The present invention relates generally to the fabrication of
composite structures and to material placement machines. More
particularly, the present invention relates to systems and methods
of detecting flaws and foreign object debris (FOD) and
characteristics thereof during the fabrication of a composite
structure.
2. Background of the Invention
Composite structures have been known in the art for many years.
Although composite structures can be formed in many different
manners, one advantageous technique for forming composite
structures is a fiber placement or automated collation process.
According to conventional automated collation techniques, one or
more ribbons of composite material, known as composite strands or
tows, are laid down on a substrate. The substrate may be a tool or
mandrel, but more conventionally, is formed of one or more
underlying layers of composite material that have been previously
laid down and compacted.
Conventional fiber placement processes in the formation of a part
utilize a heat source to assist in the compaction of the plies of
composite material at a localized nip point. In particular, the
ribbons or tows of the composite material and the underlying
substrate are heated at the nip point to increase resin tack while
being subjected to compressive forces to ensure adhesion to the
substrate. To complete the part, additional strips of composite
material can be applied in a side-by-side manner to each layer and
can be subjected to localized heat and pressure during the
consolidation process.
Unfortunately, defects can occur during the placement of the
composite strips onto the underlying composite structure. Such
defects can include tow gaps, overlaps, dropped tows, puckers, and
twists. Additionally, foreign objects and debris (FOD), such as
resin balls and fuzz balls, can accumulate on a surface of the
composite structure. Resin balls are small pieces of neat resin
that build up on the surfaces of the fiber placement head as the
pre-impregnated tows pass through the guides and cutters. The resin
balls become dislodged due to the motion and vibration of the fiber
placement machine, and drop on to the surface of the ply.
Subsequent courses of applied layers cover the resin ball and a
resultant bump is created in the laminate whereat there may be no
compaction of the tows. The fuzz balls are formed when fibers at
the edges of the tows fray and break off as the tows are passed
through the cutter assembly. The broken fibers collect in small
clumps that fall onto the laminate and are covered by a subsequent
layer.
Composite structures fabricated by automated material placement
methods typically have specific maximum allowable size requirements
for each flaw, with these requirements being established by the
production program. Production programs also typically set
well-defined accept/reject criteria for maximum allowable
cumulative defect width-per-unit-area.
Composite laminates fabricated by fiber placement processes are
typically subjected to a 100% ply-by-ply visual inspection for both
defects and FOD. Typically, these inspections are performed
manually during which time the fiber placement machine is stopped
and the process of laying materials halted until the inspection and
subsequent repairs, if any, are completed. In the meantime, the
fabrication process has been disadvantageously slowed by the manual
inspection process and machine downtime associated therewith.
Current inspection systems are capable of identifying defects in a
composite structure during the fabrication process without
requiring machine stoppage for manual inspections. The inspection
systems are capable of detecting, measuring, marking, and
identifying FOD "in-process" or during the fabrication of a
composite structure. This, in turn, eliminates the need for manual
FOD inspections and the machine downtime associated therewith.
It is desirable that an inspection system be capable of determining
characteristics of flaws and FOD, including size, location, type,
density-per-unit area, and cumulative defect width-per-unit area.
Thus, there exists a need for an improved inspection system and
method of detecting, identifying, and determining characteristics
of flaws and FOD within and during the fabrication of a composite
structure.
SUMMARY OF THE INVENTION
One embodiment of the present invention provides an inspection
system that includes an idler wheel. The idler wheel is coupled to
a fabrication system and is in contact with a backing layer of an
applied material. A rotation sensor monitors the idler wheel and
generates a rotational signal. A controller is coupled to the
rotation sensor and determines a characteristic of one or more
flaws and FOD on a composite structure in response to the rotation
signal.
The embodiments of the present invention provide several
advantages. One such advantage is the provision of a composite
structure in-process fabrication inspection technique that
accurately determines flaw and FOD characteristics.
Another advantage provided by an embodiment of the present
invention, is the provision of a composite structure in-process
fabrication inspection technique that accurately determines flaw
and FOD characteristics without actually communicating with a
material placement machine to obtain location coordinates.
Yet another advantage provided by an embodiment of the present
invention, is the provision of a composite structure in-process
fabrication inspection technique that determines the density of
flaws and FOD per unit area and the width of the flaws and FOD per
unit area.
Furthermore, another embodiment of the present invention identifies
areas of a composite structure for further analysis in view of
processing parameters, such as placement speed and programmed gap
information, and flaw and FOD trends. In analyzing processing
parameters and flaw and FOD trends one can adjust fabrication
processes to prevent future flaw and FOD occurrences.
Moreover, the present invention allows for the in-process repair of
a composite structure upon detection of a flaw or FOD.
The present invention itself, together with further objects and
attendant advantages, will be best understood by reference to the
following detailed description, taken in conjunction with the
accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side schematic view of a fabrication system
incorporating a flaw and FOD inspection system in accordance with
an embodiment of the present invention;
FIG. 2 is a block diagrammatic and perspective view of the position
detection system and components of a material placement machine in
accordance with an embodiment of the present invention;
FIG. 3 is a perspective view of an application portion of a
fabrication system incorporating a flaw and FOD inspection system
in accordance with another embodiment of the present invention;
FIG. 4 is a perspective view of light sources according to the
embodiment of FIG. 2;
FIG. 5 is a perspective view of a fabrication system incorporating
a flaw and FOD inspection system in accordance with another
embodiment of the present invention;
FIG. 6 is a logic flow diagram illustrating a method of determining
flaw and FOD characteristics during the fabrication of a composite
structure in accordance with an embodiment of the present
invention;
FIG. 7 is a ply layout illustrating course and frame locations in
accordance with an embodiment of the present invention;
FIG. 8 is a top view of a sample irregularly shaped ply in
accordance with an embodiment of the present invention;
FIG. 9 is a front view of a display and user controls illustrating
the detection of flaws and FOD and indication of flaws and FOD
characteristics in accordance with an embodiment of the present
invention; and
FIG. 10 is a logic flow diagram illustrating a method of
fabricating a composite structure in accordance with an embodiment
of the present invention.
DETAILED DESCRIPTION
In each of the following Figures, the same reference numerals are
used to refer to the same components. While the present invention
is described with respect to systems and methods of detecting flaws
and foreign object debris (FOD) and characteristics thereof during
the fabrication of a composite structure, the present invention may
be adapted for various applications and systems, such as
fabrication of structures and components, production line
applications, or other applications and systems known in the art.
The present invention may be applied to both the fabrication of
aeronautical and non-aeronautical systems and components.
In the following description, various operating parameters and
components are described for one constructed embodiment. These
specific parameters and components are included as examples and are
not meant to be limiting.
Also, in the following description the term "foreign object debris
(FOD)" refers to any resin ball, fuzz ball, impurity, backing
paper, backing film, or other foreign or undesirable object
contained within or on a composite structure. FOD may refer to one
or more of the stated objects.
In addition, the term "flaw" refers to any defect within a
composite structure or structure under fabrication. A flaw may
refer to a tow gap, an overlap of material, a dropped tow, a
pucker, a twist or any other flaw known in the art.
Referring now to FIG. 1, a side schematic view of a fabrication
system 8 is shown incorporating a flaw and FOD detection and
inspection system 9 in accordance with an embodiment of the present
invention. The fabrication system 8 includes a lamination system
10, as best seen in FIGS. 2 and 3, that may utilize an automated
collation process to form a composite structure 12, as shown. The
inspection system 9 is positioned proximate the composite structure
12 and includes one or more illumination devices or light sources
13 (only one is shown) and one or more detectors 14 (only one is
shown). The light sources 13 generate light arrays 16 that are
directed at a portion 18 of the composite structure 12 to reveal
flaws and FOD 19 within that portion 18. The inspection system 9
also includes a flaw and FOD position detection system 20, which
determines the position of the flaws and FOD 19. A controller 24 is
coupled to the detectors 14 and the position detection system 20
and interprets data received therefrom. The collected data may be
used to adjust the operation of the fabrication system 8, the
inspection system 9, and the lamination system 10, and to indicate,
detect, and allow for the correction of the flaws and FOD 19. The
controller 24 may store the received data and/or related
information in the memory or storage device 26. System parameters
and operation may be adjusted via the user interface 28.
During the fabrication of the composite structure 12, the composite
structure 12 may be formed of adjacent tows or strips of composite
tape (not shown) to form layers 29. The strips include multiple
fibers that are embedded in a resin or other material, which
becomes tacky or flowable upon the application of heat. The strips
are arranged on a work surface 30 of a table, mandrel, or tool 32,
and compacted with a compaction roller to form the composite
structure 12. A compaction roller 34 can be seen in FIG. 2. The
automated collation process includes guiding the composite strips
from material creels (not shown) to an automated collation or fiber
placement machine, such as a machine made by Cincinnati Milacron
and Ingersoll Milling Machines. In particular, the composite strips
are guided to a head unit or assembly 36, which may be best seen in
FIG. 3, and fed under the compaction roller 34. Focused heat energy
is then applied to adhere the incoming material and the underlying
previously laid material. With the combination of pressure and
heat, the composite strips are consolidated into a previous applied
layer to form an additional layer on the composite structure
12.
An example of an automated collation technique that may be used is
described in U.S. Pat. No. 6,799,519 B2, entitled "Composite
Material Collation Machine and Associated Method for High Rate
Collation of Composite Materials." The contents of U.S. Pat. No.
6,799,519 B2 are incorporated herein by reference.
Referring now to the inspection system 9, the light sources 13 are
positioned to emit light arrays at the selected portion 18 of the
composite structure 12. The light sources may be positioned at
various angles as known in the art, depending on the application.
Any number of light sources may be utilized even though a specific
number is shown.
The light sources 13 are positioned relative to the composite
structure 12 via a mounting apparatus 40. The mounting apparatus 40
includes a main shaft 42, a secondary shaft 44, and a locking clamp
46 for adjusting the position of the light sources 13. The mounting
apparatus 40, in turn, can be attached to the frame 48, to the
detectors 14, to the bracket 50, or to some other object that
defines a common position for both the light sources 13 and the
detectors 14 to maintain a constant spatial relationship relative
to one another.
The light sources 13 may be selected from an infrared light or
another type of light having an infrared component, such as a
halogen light source or other incandescent light sources. In other
embodiments, the light sources 13 are in the form of a fluorescent
light source (e.g., white light LEDs, a low pressure/mercury filled
phosphor glass tube, etc.), a strobe or stroboscopic light source,
a noble gas arc lamp (e.g., xenon arc, etc.), a metal arc lamp
(e.g., metal halide, etc.), or a laser (e.g., pulsed laser, solid
state laser diode array, infrared diode laser array, etc.). The
light from the light sources 13 may pass through optical fibers to
the point of delivery, an example of which is shown in FIG. 5. The
light sources 13 may include LEDs arranged in an array or cluster
formation. In one specific embodiment, the light sources 13 include
twenty-four LEDs mounted in an array upon a three-inch square
printed circuit board.
In some embodiments, the light sources 13 are operated at a power
level that increases the infrared (IR) component of the light
arrays, which aids in the inspection of dark tow material, such as
carbon. In this regard, exemplary power levels in the range of
approximately one hundred fifty watts (150 W) and in the wavelength
range of about seven hundred nanometers to one thousand nanometers
(700 nm-1000 nm) may be used. However, the particular power levels
and wavelengths for the light sources 13 depends at least in part
on the speed and sensitivity of the detectors 14, the speed at
which the material is being laid, the light delivery losses, and
the reflectivity of the material being inspected.
The detectors 14 may be of various types and styles. A wide range
of detectors may be used including commercially available cameras
capable of acquiring black and white images. In one embodiment, the
detectors 14 are in the form of a television or other type of video
camera having an image sensor (not shown) and a lens 13 through
which light passes when the cameras are in operation. Other types
of cameras or image sensors can also be used, such as an
infrared-sensitive camera, a visible light camera with
infrared-pass filtration, a fiber optic camera, a coaxial camera, a
charge coupled device (CCD), or a complementary metal oxide sensor
(CMOS). The detectors 14 may be positioned proximate the composite
structure 12 on a stand (not shown) or mounted to the frame 48 or a
similar device. In embodiments of the present invention that do not
include a reflective surface, the detectors 14 may be positioned
approximately six inches from the top surface 52 of the composite
structure 12, and mounted to the frame 48 by way of the bracket 50
and associated connectors 54. Also, any number of detectors may be
utilized.
The controller 24 may be microprocessor based such as a computer
having a central processing unit, memory (RAM and/or ROM), and
associated input and output buses.
The controller 24 may be a portion of a central main control unit,
be divided into multiple controllers, or be a single stand-alone
controller as shown.
The connectors 54 may be rivets, screws, or the like and used to
mount the detectors 14 to the frame 48 in a stationary position.
Alternatively, the connectors 54 may be a hinge-type connector that
permits the light sources 13, the detectors 14, and associated
assembly to be rotated away from the composite structure 12. This
embodiment is advantageous in situations when there is a desire to
access parts of the material placement device that are located
behind the detectors 14 and associated assembly, such as during
maintenance, cleaning, or the like.
The inspection system 9 may also include filters 56 (only one is
shown), which may be utilized in conjunction with the lens 58 for
filtering the light passing therethrough. In one embodiment, the
filters 56 are designed to filter the light such that the infrared
component of or a certain infrared wavelength or range of
wavelengths of the light is able to pass into the detectors 14.
Thus, the filters 56 may prevent ambient visible light from
entering the detectors 14 and altering the appearance of the
captured image.
Other methods of filtering light can also be used to achieve the
same, or at least used to provide a similar result. For example,
the detectors 14 may be designed to include a built-in filter of
equivalent optical characteristics. In addition, the filter 56 may
be located between the lens 58 and the detectors 14. Alternatively,
the detectors 14 may include image sensors that are sensitive in
the infrared spectrum (i.e., an infrared-sensitive camera), thus
eliminating the need for the filters 56.
The inspection system 9 may also include a marking device 60 for
marking the location of the defects and the FOD on the composite
structure 12. The marking device 60 may be attached to the frame 48
and be triggered by the controller 24 or similar device when a flaw
or FOD is detected. The marking device 60 may deposit ink, paint,
or the like onto the composite structure 12 in areas where flaws
and FOD have been detected. The markings on the composite structure
12 enable the location of the flaws and FOD to be subsequently and
readily identified either automatically or manually. The marking
device 60 may also be adapted to mark flaws with different colored
ink than that used to mark FOD. Alternatively, other marking or
indicating methods can also be used, such as markings utilizing a
pump-fed felt-tip marker or a spring-loaded marking pen,
indications via audio or visual alerts, and the like.
Referring now also to FIG. 2, a block diagrammatic and perspective
view of the position detection system 20 and components of a
material placement machine are shown in accordance with an
embodiment of the present invention. The position detection system
20 includes a material collection device 61, an idler wheel 62, and
an idler wheel rotation sensor 63. The composite material 64 having
a backing layer 65 is directed around the compaction roller 34 and
adhered to the composite structure 12. As the composite material 64
reaches the compaction roller 34 it is heated and adhered to the
composite structure 12. As the composite material 64 adheres to the
composite structure 12 the backing layer 65 is pulled from the
composite material 64, rolled around the compaction roller 34,
around the return roller 66, over the idler wheel 62, and into the
material collection device 61. The backing layer 65 may be in the
form of a backing paper, as shown, or may be in some other form
known in the art. The compaction roller 34 and the return roller 66
are part of a material placement machine or lamination system 10,
the entirety of which is not shown. The lamination system 10 may be
separate from the inspection system 9 and the position detection
system 20.
The material collection device 61 may be in the form of a
collection retainer, as shown, may be in the form of a material
collection wheel, a take-up reel, a combination thereof, or may be
in some other form known in the art.
The idler wheel 62 rests against the backing layer 65 and rotates
as the backing layer 65 passes thereon. Motion of the backing layer
65 indicates that placement of the composite material 64 is in
progress. The idler wheel 62 is free to rotate and may apply little
to no pressure on the backing layer 65. The idler wheel 62 is
coupled to the lamination system 15 and is suspended via an idler
arm 67. The idler arm 67 may be position adjustable and pressure
adjustable relative to the backing layer 65. The idler wheel may be
keyed, such that the controller 24 may capture an image of the
composite material 64 as it is applied for a predetermined number
of idler wheel revolutions.
The rotation sensor 63 is proximate the idler wheel 62 and is
coupled to the idler arm 67. The rotation sensor 63 monitors the
rotation of the idler wheel 62 and generates a rotation signal
indicative thereof. The rotation sensor may be in the form of an
encoder, an infrared sensor, a rotary potentiometer, or other
sensor known in the art that is capable of detection rotative
position and velocity of the idler wheel 62.
The position detection system 20 may also include a collection
roller 68 and a second rotation sensor or collection sensor 69. The
collection roller is coupled to the collection device 61. The
backing layer 65 is passed over the collection roller and into the
collection device 61. The second rotation sensor 69 is proximate
the collection roller 68 and detects the rotational position and
velocity of the collection roller 68.
Although a return roller 66 is shown, this is intended as one
possible example. A material placement machine may include a
moveable compaction roller or a stationary show, as known in the
art.
Referring now to FIGS. 3 and 4, a perspective view of an
application portion of a fabrication system 8 incorporating a flaw
and FOD inspection system 9' and a perspective view of light
sources 13' are shown in accordance with another embodiment of the
present invention. The inspection system 9' includes two light
sources 13' (only one is shown) positioned relative to the
composite structure 12 and the compaction roller 34 on either side
of a reflective surface 70 and a detector 14'. FIG. 3 illustrates
an alternative embodiment of the hinge-type connector 54 that
mounts the light sources 13', the detector 14', the reflective
surface 70, and associated head assembly 36 to the frame 48 by way
of the bracket 50.
The light sources 13 and 13' and the detectors 14 and 14', of FIGS.
1 and 3, may be translated or moved relative to a composite
structure, such as the composite structure 12. The adjustability
and moveability of the light sources 13 and 13' and detectors 14
and 14 provides flexibility in the capture of images of a composite
structure. Sample systems including moveable cameras and light
sources are described in detail in previously referred to U.S.
patent application Ser. No. 10/217,805.
Although the light sources 13' are shown in the form of four
halogen light bulbs 74, other quantities, types, and styles of
illumination sources may be utilized. A light reflection element 76
is located near the light sources 13'. The reflection element 76
includes a series of light reflecting surfaces 78 that redirect the
light towards the desired area to be illuminated. This levels the
illumination across the top surface of a composite structure and
eliminates, or at least substantially reduces, the areas of intense
light (i.e., hotspots) created by the brightest portion of the
light source. Hotspots can lead to errors during the processing of
images. The light reflection elements 78 are particularly
advantageous for illuminating the curved/contoured surfaces of the
composite structures because the redirection of the light permits a
larger portion of a composite structure to be evenly
illuminated.
The reflection element 76 is curved around the light sources 13',
such as in a parabolic shape. The reflection elements 78 are in the
form of curved steps that are substantially parallel to the light
source 13'. The distance between and the curvature of the
reflection elements 78 may be selected for sufficient and even
illumination generated from the sum of the two light sources 13'.
This enables more consistent illumination of the composite
structure 12, which prevents, or at least reduces, the
image-processing errors due to inconsistent illumination of the
composite structure 12. Alternatively, the shape and/or surface
configuration of the reflection elements 78 may be modified using
other techniques known in the art to produce consistent
illumination and scattering of light.
In an exemplary embodiment, seventeen reflection elements are
utilized and have an overall parabolic shape and a range of widths
from about 0.125 inches at the outer edge of the reflection
elements to about 0.250 inches at the center of the reflection
elements. The reflection elements also have a uniform step height
of about 0.116 inches. In other embodiments, however, the
reflection elements 78 may be provided with different numbers of
steps having different uniform or varying widths and different
uniform or varying step heights.
Furthermore, the reflection elements 78 may be adjusted in order to
direct the light produced by the light sources 13' and scattered by
the reflection elements 78 toward the selected portion of a
composite structure. For example, as shown in FIG. 4, the
reflection elements 78 are mounted to the mounting apparatus 40
with fasteners 80. The fasteners 80, when loose, are capable of
being slid within slots 82 to correspondingly adjust the angle of
the reflection elements 78 relative to a composite structure. Once
the reflection elements 78 are positioned appropriately, the
fasteners 80 are tightened to secure the reflection elements 78 in
the desired position. Adjustments of the reflection elements 78 can
also be enabled by other methods, such as by electronic means that
permit remote adjustment of the reflection elements 78.
The detectors 14 are positioned near the composite structure 12 and
when in the form of cameras are positioned to capture images of the
selected illuminated portion, which is typically immediately
downstream of the nip point at which a composite tow is joined with
the underlying structure.
The light sources 13, the detectors 14, the reflective surface 16,
and any reflection elements 78, may be mounted on the head unit 23
to allow for continuous capture of real-time data of the composite
structure 12. The real time data may be captured as the head unit
36 is transitioned across the composite structure 12 and as the
composite strips are laid down or applied.
The bracket 50 may be fastened to the hinge type connector 54 via a
suitable fastener, such as a thumbscrew or any other fastener that
may be utilized and inserted through hole 72 and then tightened to
secure the assembly in place for operation. The fastener may be
loosened or removed, for example, to rotate the light source and
detector assembly away from the compaction roller 34 and other
parts of the fabrication system.
The reflective surface 70 may be positioned near the composite
structure 12, and angled such that the reflective surface 70
reflects an image of the illuminated portion to the detectors 14.
In one embodiment, the angle of the reflective surface 70 to the
composite structure is about sixty-five degrees, but the reflective
surface 16 can also be positioned at any appropriate angle in order
to reflect images of the illuminated portion to the detectors 14.
The detectors 14 may be positioned to point toward the reflective
surface 70 in order to capture the close-range images of the
illuminated portion from the reflective surface 70. More than one
reflective surface 70 may also be utilized in further embodiments
of the present invention in which the reflective surface 70
cooperate in order to direct the images of the illuminated portion
to the detectors 14.
The reflective surface 70 may be in various positions relative to a
selected portion, such as portion 18. Reflective surface 70 can
also be utilized to allow the detectors 14 to be placed in an
advantageous positions, which might otherwise be blocked by
portions of the compaction roller 34 and/or other parts of the
fabrication system.
The configuration illustrated in FIG. 3 aids in the capturing of
images of curved/contoured surfaces of a composite structure since
the reflective surface 70 is positioned close to the composite
structure. In addition, this configuration permits the detectors 14
to be positioned away from a composite structure, to prevent
interference between the detectors 14 and components of the
fabrication system 8'. Further, the reflective surface 70 can also
provide a "square on" view of the selected portion being inspected,
which, in turn, can improve the ability to dimension the two gaps
for pass/fail decisions.
Referring now to FIG. 5, a perspective view of a fabrication system
8'' incorporating a flaw and FOD inspection system 9'' in
accordance with another embodiment of the present invention is
shown. The inspection system 9'' includes lights sources (not
shown) that are at a remote location. The light sources generate
light rays, which are passed through linear optical fiber arrays or
fiber optic cable 90 to point of transmission 92 via light emitting
heads 94. Light arrays are emitted from the fiber optic cable 90
toward the selected portion 18' of the composite structure 12' to
detect flaws and FOD 19'. The use of fiber optic cables simplifies
the number of components mounted on the head assembly.
Referring now to FIGS. 6 and 7, a logic flow diagram illustrating a
method of determining flaw and FOD characteristics during the
fabrication of a composite structure and a ply layout illustrating
course and frame locations are shown in accordance with an
embodiment of the present invention.
In step 95, strips of the composite material 64 are applied to the
tool 32 to form the composite structure 12.
In step 96, as the strips are applied, the backing layer 65 is
removed from the composite material 64 in turn causing the idler
wheel 62 to rotate.
In step 97, the rotation sensors 63 and 69 generate the rotation
signals that are indicative of the rotational position and velocity
of the idler wheel 62 and the collection roller 68. The rotational
signals are also indicative of any cessation in the backing layer,
such as when the lamination system 10 or the application position
of the composite material 64 is laterally transitioned to form
another column or course. Cessation of motion indicates that
material lay-down for the current course has stopped and that a new
course may be started. The rotational signals may be compared,
averaged, and utilized to accurately determine position of the
lamination system 10. The rotational signals may also be utilized
to determine when the backing layer is "bunching up" or not passing
through the fabrication system appropriately.
FIG. 7 illustrates a sample single ply 98 of a rectangular
composite structure 99 with frame rows 100 and courses 101. Seven
rows of sixteen courses are shown. Of course, any number of rows
and courses may be created. Also each ply, such as ply 98, may be
of various shape, another example of which is shown in FIG. 8. The
ply 98 is divided into multiple unit areas 102, each of which
corresponding to an image frame. Each unit area 102 may have a
width w greater than the width of the strips (not shown) of the
composite material being applied and a height h that corresponds to
a determined number of revolutions of the idler wheel 62. In one
embodiment, the unit area width w is approximately equal to seven
inches, the width of the composite material plus a half of an inch
for each side of the material. In another embodiment, the height h
is approximately seven inches corresponding to the circumference of
the idler wheel 62. The frame numbers may be sequentially assigned
even when the course number changes.
In step 104, the portion 18 of concern is selected. The portion 18
may include the entire composite structure under formation or may
include a discrete segment or area of the composite structure. In
step 105, the light sources 13 are activated to illuminate the
selected portion 18. The light rays 16, which may be in the form of
arrays, are generated such that both the flaws and FOD 19 may be
detected simultaneously within the selected portion 18. The light
sources may be activated throughout the material placement
process.
In step 106, detectors, such as detectors 14 and 14', monitor the
portion 18 and generate status signals in response to the
reflection of the light rays 16 off of the portion 18. The status
signals contain information regarding the existence of flaws and
FOD in the portion 18. The detectors 14 and 14' detect light
reflection characteristics of the flaws and FOD.
In step 107, the controller 24 determines one or more flaw and FOD
characteristics in response to the rotation signal and the division
of the current ply. The characteristics may be determined during
the application of the composite material 64. The flaw and FOD
characteristics may include size, location, position, type,
density-per-unit area, cumulative defect width-per-unit area, and
any other flaw and FOD characteristic known in the art. Width
information of flaws and FOD provides gap and density information.
Manufacturing specifications that govern automated material
placement have acceptance requirements for various types of
defects. For gaps there is a maximum allowable width for a single
gap and a maximum allowable total width for of all of the gaps
existing within a defined area. Likewise, for FOD there is a
maximum allowable number of occurrences with a defined area. Thus,
the detector 14 and/or the controller 24 may track the area that
has been inspected and the number and total width of flaws that
have been detected.
For example, the controller may determine longitudinal and lateral
position of a flaw or FOD in response to the number of frames
captured in a given row and the number of detected cessations per
ply. The detector 14 or the controller 24 may store an image after
a preset number of revolutions of the idler wheel 62. The number of
revolutions remains constant and establishes the image frame
height. This along with the constant width of the material course
being placed establishes a constant rectangle, referred to as a
frame. The frames are tracked by assigning a discrete number to
each frame.
In step 107 A, the controller 24 generates an image count for each
of the flaws and FOD to determine a linear distance to each of the
flaws and FOD. The image count provides a course measurement of
longitudinal position. In step 107 B, the controller 24 generates a
revolution count indicative of the revolutions of the idler wheel
62, which is indicative of the position of the lamination system
and any detected flaws and FOD in that position. The revolution
count provides a fine measurement of longitudinal position within
an image frame. In step 107 C, the controller 24 generates a
cessation count for each of the flaws and FOD. In step 107 D, the
controller 24 may also generate an applied layer or ply count
indicative of the number of currently applied plies. In step 107 E,
the controller 24 determines the position of the flaws and FOD in
response to the image count, the revolution count, the cessation
count, and the ply count.
In step 107 F, the controller 24 determines the flaw areal density.
In step 107 F 1, the controller 24 counts the flaws and FOD in a
current frame to generate a current flaw and FOD frame count. In
step 107 F 2, the controller 24 sums the current flaw and FOD frame
count with flaws and FOD of two adjacent frames of a previous
course to generate a resultant sum. In step 107 F 3, the controller
24 determines flaw areal density for the portion in response to the
resultant sum. The flaw areal density is equal to the resultant sum
divided by the area of the portion.
In step 107 G, the controller 24 determines size of the flaws and
FOD. In step 107 H, the controller 24 determines cumulative gap
width per unit area in response to the portion 18, the frame, or a
current set of frames and the size.
In step 108, the detected flaws and FOD 19 as well as the related
characteristics thereof are indicated to a user via a display, such
as that shown with respect to FIG. 9.
In step 109, the flaw and FOD characteristics as detected may be
stored in an archival error file within the memory 26, such as in
an error file. The characteristics may include the ply, course, and
frame number associated with each flaw and FOD. Also, after a
preset number of revolutions the detectors 14 or the controller 24
may store images of the portion 18 within the memory 26. Since the
frame size is constant it is possible to establish the location of
a defect on the surface by counting frames from an initial starting
point. The detector 14, the controller 24, or other device that has
access to the stored information may determine approximate location
of each flaw and FOD therefrom separate from and without being
hard-wired to the fabrication system 8 and/or the material
placement machine, stated with respect to FIG. 2.
Referring now to FIG. 8, a top view of a sample irregularly shaped
ply 110 is shown. The length of the courses 111 vary over the ply
110 and thus the image frames, corresponding to unit areas 112, are
staggered. When a course ends in an angular cut, the last frame in
that course may be assumed to be fully rectangular in shape for the
purpose of designating a unit area. Flaw and FOD characteristics
may be determined in response to the frame stagger. In the example
embodiment, the unit areas 112 and thus the frames are in a 50%
stagger. Each unit area is bordered by half portions of two
adjacent unit areas. The unit areas and the frames may be oriented
at any staggered percentage.
When determining flaw areal density, the number of flaws in any
affected frame (diagonally cut frame) is summed with those in two
adjacent frames of a previous course instead of one. Cumulative gap
width is determined by measurement across a designated area in a
direction perpendicular to the direction of material placement on a
tool. For summation purposes the gaps may be assumed or assigned to
extend an entire length of the affected image frames, such that
location within a frame of gap location is unnecessary.
Positions of the flaws and FOD may be determined utilizing
information from archived positions and engineering disposition and
may be resolved utilizing known in-process flaw and FOD marking
techniques.
Referring now to FIG. 9, a front view of a user display screen 120
and user controls 122 illustrating the detection of flaws and FOD
124 and indication of flaws and FOD characteristics in accordance
with an embodiment of the present invention is shown. Although the
operation and use of the display 120 is primarily described with
respect to the embodiment of FIG. 1, it may be easily modified for
and applied to other embodiments of the present invention. The user
interface 28 includes the display 120, such as that on a computer
monitor, and can also include an input device, such as a keyboard
and mouse (not shown), for permitting an operator to move a cursor
about the display 120 and input various system settings and
parameters. The display 120 may be touch-sensitive for permitting
the operator to input the desired settings by manually touching
regions of the display screen.
The interface 28 includes an image window 126 in which an image
128, of the composite structure 12, is displayed for viewing by an
operator or other user. The image 128 may be in the form of an
unprocessed or processed camera image. When processed the image 128
or a portion thereof may be binarized. During binarization, all
shades of gray above a predetermined threshold value may be changed
to white, while all gray shades below the threshold value may be
changed to black to heighten the contrast of defects and improve
the accuracy of defect detection. As an alternative or in addition
to binarization, rates of light level change in the raw image and
color changes in the images may be used to identify the defects and
FOD.
The interface 28 also includes a position window 129, which may
display the ply number, course number, and frame number of the
lamination system in a current state as is related to a currently
viewed image.
The controls 122 allow for various user inputs to the system. The
controls 122 may be used to adjust the binarization threshold.
Generally, the setting of the binarization threshold involves a
tradeoff between the sensitivity with which defects are detected
and the resolution with which the defects are depicted. In one
embodiment, the binarization threshold is set to about 128, which
corresponds to the mid-point on the 8-bit digitizing range of 0 to
255. However, other binarization threshold values may be employed
depending at least in part on the particular application, available
lighting, camera settings, and other factors known in the art.
The controls 122 also allow the user to adjust or shift the viewing
area within the window 126. During operation, the window 126
displays real-time moving video images of the illuminated portion
of the composite structure 12 as the detectors 14 and/or the
reflective surface 18 are moved relative to the composite structure
12. The controls 122 may be such to allow the user to input the
maximum allowable dimensional parameters, the acceptable
tolerances, as well as other known parameters for the flaws and
FOD.
In addition to displaying images of the composite structure 12, the
display screen 80 may also include a defect table 128, which lists
the discovered flaws and FOD and provides related information
thereof, such as location, size, and the like. The display 120 can
further include status indicators 130 that notify the user whether
a particular image area is acceptable or not acceptable based on
predefined criteria, such as the maximum allowable dimensional
parameters and tolerances.
Referring now to FIG. 10, a logic flow diagram illustrating a
method of fabricating a composite structure in accordance with an
embodiment of the present invention is shown. Although the logic
flow diagram of FIG. 10 is primarily described with respect to the
embodiment of FIG. 1, it may be easily modified to apply to other
embodiments of the present invention.
In step 150, the fabrication system 8 applies the strips to form
the layers 29 on the substrate 32 to form the composite structure
12. In step 152, the inspection system 9 illuminates selected areas
of or the entire composite structure 12 during the application of
the strips to detect the flaws and FOD 19 as described above with
respect to the method of FIG. 5. Flaws and FOD may be detected
continuously throughout the material placement process and
continuously over selected portions or the entire composite
structure 12.
In step 154, the inspection system 9 distinguishes, identifies, and
determines characteristics of the flaws and FOD 19 and the location
thereof and generates a composite structure defect signal. Examples
regarding systems and methods for identifying defects in a
composite structure during fabrication thereof are included in U.S.
patent application Ser. No. 09/819,922, filed on Mar. 28, 2001,
entitled "System and Method for Identifying Defects in a Composite
Structure" and in U.S. patent application Ser. No. 10/217,805,
filed on Aug. 13, 2002, entitled "System for Identifying Defects in
a Composite Structure". The contents of U.S. patent application
Ser. Nos. 09/819,922 and 10/217,805 are incorporated herein by
reference as if fully set forth herein.
In step 156, the fabrication system 8 may in response to the
composite structure defect signal alter the operation thereof. The
fabrication system 8 may cease further application of the strips
until one or more portions of the composite structure 12 are
repaired, may alter the manner in which the strips are applied, may
adjust parameters of the fabrication system 8 or inspection system
9, or may perform other tasks known in the art.
At any time upon or after the generation of the status signals
and/or the defect signals the controller 24 may store data or
images in the storage device 26 for future or off-line analysis
and/or processing. Future analysis may be based on processing
parameters, such as material placement speed and programmed gap
information, and flaw and FOD trends.
The above-described steps in the methods of FIGS. 5 and 8, are
meant to be illustrative examples, the steps may be performed
synchronously, continuously, or in a different order depending upon
the application.
The present invention provides systems and methods for the
simultaneous detection of flaws and FOD using a single illumination
level. The present invention simplifies the detection of the flaws
and FOD and allows for efficient identification and repair
thereof.
While the invention has been described in connection with one or
more embodiments, it is to be understood that the specific
mechanisms and techniques which have been described are merely
illustrative of the principles of the invention, numerous
modifications may be made to the methods and apparatus described
without departing from the spirit and scope of the invention as
defined by the appended claims.
* * * * *
References